Greetings All, my son just got a bike. The engine is a two stroke, identical to the two strokes that Im seeing on the pics here and other sites. I'm want to determine the engine size so that I can get replacement piston and rings, and / or cylinder if needed. All I can tell you now is the piston's diameter is about 1 13/16 " . The guy he bought it from said it's an 80 CC but I want to be sure of the size before I buy any parts. Is there any thing else I can give that would help determine the engine size. Any help would be much appreciated
Trying to Figure Engine Size
- Thread starter JIM E
- Start date
Dave31
Active Member
Welcome to the forum JIM E...
Formula to figure engine cc displacement;
( multiply 3.142 x radius of bore mm squared x stroke length mm divided by 1000. )
To figure displacement for this example: 47mm bore x 38mm stroke;
Bore diameter divided by 2 = 23.5 mm radius
To square radius multiply 23.5mm x 23.5mm = 552.25 radius mm squared
552.25mm x 3.142 = 1735.17mm
1735.17mm x 38mm = 65936 cubic milliliters;
To get cubic centimeter divide 65936 by 1000 = 65.936cc or round off to 66cc
Formula to figure engine cc displacement;
( multiply 3.142 x radius of bore mm squared x stroke length mm divided by 1000. )
To figure displacement for this example: 47mm bore x 38mm stroke;
Bore diameter divided by 2 = 23.5 mm radius
To square radius multiply 23.5mm x 23.5mm = 552.25 radius mm squared
552.25mm x 3.142 = 1735.17mm
1735.17mm x 38mm = 65936 cubic milliliters;
To get cubic centimeter divide 65936 by 1000 = 65.936cc or round off to 66cc
Al.Fisherman
New Member
My thing fits perfect in a 49cc engine, whereas the 66.5 is too large. (joke)
Only 2 sizes a 49cc and a 66.5 (80)cc The bore on a 66.5 is 1 + 7/8 inches.
Only 2 sizes a 49cc and a 66.5 (80)cc The bore on a 66.5 is 1 + 7/8 inches.
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